Evaluation of Body Position Association with Diuretic Response and Neurohormonal Activation in Patients with Acutely Decompensated Heart Failure.

Background/Objectives: Hemodynamic and neurohormonal factors, including renal perfusion and venous pressure, may affect diuretic response, which may be modulated by body position. This study aimed to assess whether supine versus upright positioning influences diuretic efficacy and neurohormonal activation during early decongestion in patients with AHF and reduced ejection fraction (HFrEF). Methods: This single-center, prospective, pilot randomized study enrolled 12 hospitalized patients with decompensated HFrEF receiving guideline-directed medical therapy. Participants were randomized (1:1) to remain in either the supine or upright/seated position during intravenous furosemide administration (1 mg/kg: half of the dose administered as a bolus, half as a 2-h infusion). Serial measurements of urine volume, electrolyte excretion, and neurohormonal biomarkers (renin, aldosterone, catecholamines) were performed at baseline, 2, and 6 h after diuretic administration. Results: No significant differences were found between supine and upright groups in total urine output, urine dilution, sodium excretion, or weight change after 6 h. There were no statistically significant differences in renin and aldosterone levels across subsequent timepoints; however, renin concentration tended to be higher in upright than in supine individuals. Interestingly, supine participants demonstrated greater urinary adrenaline concentration after furosemide administration, alone and after adjustment for urinary creatinine. Conclusions: No clinically meaningful differences were found between supine versus upright position patients with AHF, receiving neurohormonal blockade.